Examining the impact of depth to groundwater table on evapotranspiration in a semi-arid grassland region
Abstract
A number of recent numerical modeling studies have demonstrated a strong control of shallow groundwater table on evapotranspiration and land surface-atmosphere interactions. It has been previously shown that neglecting the role of groundwater in land surface models may result in significant errors in the surface energy and water balance, especially in areas where the water table is shallow. Despite the importance of groundwater on land surface processes predicted by numerical models, there is little experimental evidence supporting such model predictions. In this study, we examine the role of regional groundwater table on growing season evapotranspiration fluxes in the Sand Hills region of Nebraska, USA, which is the major recharge zone of the Ogallala aquifer. Historical data on depth to water table (DWT) in 239 wells have been obtained from the publically available USGS, National Water Information System web site. Evapotranspiration (ET) and potential evapotranspiration (PET) at a 1 km grid resolution have been obtained from the MODIS (MOD16) global evapotranspiration products from 2000 to 2010. Precipitation over the growing season is quantified from the PRISM data. Wells located within irrigated croplands along main valleys in the region are eliminated from the analysis. Our preliminary results revealed controls of DWT on both ET/PET and ET/P ratios. Consistent with some modeling studies, evapotranspiration significantly grew when DWT is within 10 meters below the land surface. These findings have important implications for delineating regions where groundwater influence on land surface fluxes could be substantial.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H41E1098A
- Keywords:
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- 1818 HYDROLOGY / Evapotranspiration;
- 1819 HYDROLOGY / Geographic Information Systems;
- 1830 HYDROLOGY / Groundwater/surface water interaction;
- 1843 HYDROLOGY / Land/atmosphere interactions